For a single platform, PredictionHero does not calculate the probability itself. It's derived directly from that platform's market price. Since each platform may use different pricing mechanisms or have different liquidity, probabilities can vary slightly across platforms, and PredictionHero displays these side by side for easy comparison.
For a cross-platform view, PredictionHero does calculate its own consensus figure, recalculated every 15 minutes from the underlying platform data.